1. Field of the Invention
The invention relates to a process for distributing unique number identifiers called tickets in a multi-node data processing system. A multi-node data processing system is composed of remote data processing systems called nodes, interconnected with one another by electrical or optical transmission links.
The invention is particularly adapted to multi-node data processing systems wherein the nodes each run their own operating system and/or each have several processors, thus constituting multiprocessor multi-mode systems, and/or the links are dedicated to communication between these nodes. The links can convey messages either in the form of serial bit streams (serial links) or in the form of successive bit slices disposed in parallel (parallel links).
Corollary objects of the invention are a multi-node data processing system which implements the process, as well as a data processing node and an integrated circuit for implementing the process or the data processing system.
2. Description of Related Art
For purposes of programming multi-task applications, it may be necessary to dynamically assign an identifier to a task or a time label or time stamp to an event.
It is understood that in order to distinguish a task from other tasks, the identifier of the task must be unique within the system. Likewise, in order to distinguish the position of an event in the time sequence of events, the time stamps must be ordered.
The identifiers and the time stamps can be obtained from a mechanism provided by the system. The function of this mechanism is to deliver, in response to a request for an identifier or a time stamp, a number which is unique in the space and which lasts for enough time to prevent any error. This number corresponds to a numeral and is called a ticket, and the mechanism provides a ticket distribution service. A ticket is usually distributed in a determined order, which is increased or decreased in a monotonic way according to the temporal order of the requests for tickets. The distribution of the tickets is ordinarily performed by a software component.
This software component manages the distribution of the tickets in a centralized way. This centralization requires communication between the operational software requesting a ticket and the software ticket distribution component. This involves internodal software and hardware communication mechanisms which carry out the execution of protocols and the physical transfer of data. In practice, passage through internodal communications management software complicates the operational software of the system and slows down the distribution of the tickets.
Moreover, there is currently increasing demand for a multi-node data processing system with high availability. This quality means that the system must retain its functionalities in spite of the occurrence of a hardware or software malfunction, or even a loss of part of the system, the loss of a node, for example. In this case, it is essential that the distribution of the tickets also retain its functionality. The software solution consists of distributing the distribution service among the nodes or of duplexing the service. These two solutions require additional internodal communications in order to ensure the consistency of the distribution of tickets throughout the system. This further complicates the operational software of the system. Moreover, by increasing the number of internodal communications, the software substantially slows the distribution of tickets.